Arthropod anatomy

The trachea (: tracheae or tracheas), also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all land vertebrate animals' lungs. The trachea extends from the larynx and branches into the two primary bronchi. At the top of the trachea, the cricoid cartilage attaches it to the larynx. The trachea is formed by a number of horseshoe-shaped rings, joined together vertically by overlying ligaments, and by the trachealis muscle at their ends. The epiglottis closes the opening to the larynx duri

thumb|right|The red gills of this common carp are visibly exposed as a result of a gill flap [[birth defect.]] A gill () is a specialized respiratory organ that many aquatic animals use for aquatic gas exchange, i.e. to extract dissolved oxygen from water and to excrete carbon dioxide. Branchia (: branchiae, from Ancient Greek ) is the zoologists' academic name for gills.

appendages used for sensing in arthropods

thumb|Collection of hemolymph from a worker honeybee.

arthropod eye

thumb|Bauplan of a [[malacostracan; the cephalothorax is the region including cephalon and thorax, marked in yellow.|upright=1.2]] The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms prosoma and opisthosoma are equivalent to cephalothorax and abdomen in some groups. The terms prosoma and opisthosoma may be preferred by some researchers in cases such as arachnids, where there is neither fossil nor embryonic evidence animals in this class have ever had separate

excretory and osmoregulatory system

grouping of multiple anatomical segments forming a morphological unit (e.g. of an insect)

thumb|Fiddlers crabs like Minuca pugnax, and other members of the family [[Ocypodidae, have chelae of different sizes: a large left chela and a small right chela.]]

upright=1.4|thumb|right|Diagram highlighting the telson of the prawn Litopenaeus setiferusthumb|Telson (arrow no. 3) of the horseshoe crab Carcinoscorpius rotundicauda

The nephridium (: nephridia) is an invertebrate organ, found in pairs and performing a function similar to the vertebrate kidneys (which originated from the chordate nephridia). Nephridia remove metabolic wastes from an animal's body and come in two basic categories: metanephridia and protonephridia. In some cases, nephridia may fuse or become functionally integrated with coelomoducts—mesodermal structures that open from the coelom to the exterior—to form a more complex structure known as a nephromixium. All animals possessing nephridia or kidneys belong to the clade Nephrozoa.

thumb|right| Ommatidium: A – cornea, B – crystalline cone, C & D – pigment cells, E – rhabdom, F – photoreceptor cells, G – membrana fenestrata, H – optic nerve thumbnail|Ommatidia of a krill The compound eyes of arthropods like insects, crustaceans and millipedes are composed of units called ommatidia (: ommatidium). An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. The outer part of the ommatidium is overlaid with a transparent cornea. Each ommatidium is innervated by one axon bundle (usually consisting of 6–9 axons, depending on the numbe

thumb|right|alt=|Drawing of the statocyst system thumb|Statocysts (ss) and statolith (sl) inside the head of sea snail Gigantopelta chessoia

thumb|right|The exoskeleton of a [[spiny lobster is made of a series of sclerites, connected by flexible joints.]] A sclerite (Greek , ', meaning "hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonly to the hardened parts of arthropod exoskeletons and the internal spicules of invertebrates such as certain sponges and soft corals. In paleontology, a scleritome''' is the complete set of sclerites of an organism, often all that is known

opening in the exoskeletons of some arthropods

thumb|Tergites (with lateral paranota) of a Polydesmida|polydesmid millipede A tergum (Latin for "the back"; : terga, associated adjective tergal) is the dorsal ('upper') portion of an arthropod segment other than the head. The anterior edge is called the 'base' and posterior edge is called the 'apex' or 'margin'. A given tergum may be divided into hardened plates or sclerites commonly referred to as tergites.

thumb|The ventral side (underside) of a female American lobster, a member of the class [[Malacostraca. The gonopores are at the bases of the third walking leg, pointing towards the animal's tail.]] A gonopore, sometimes called a gonadopore, is a genital pore in many invertebrates. Hexapods, including insects, have a single common gonopore, except mayflies, which have a pair of gonopores. More specifically, in the unmodified female, it is the opening of the common oviduct, and in the male, it is the opening of the ejaculatory duct.

The hepatopancreas, digestive gland or midgut gland is an organ of the digestive tract of arthropods and molluscs. It provides the functions which in mammals are provided separately by the liver and pancreas, including the production of digestive enzymes, and absorption of digested food.

right|thumb|222px|Diagram showing the location of the Cephalon (arthropod head)|cephalon, [[thorax and pygidium of a trilobite.]] The pygidium (: pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is composed of fused body segments, sometimes with a tail, and separated from thoracic segments by an articulation.

thumb|Scorpion anatomy: 1 = prosoma; 2 = mesosoma; 3 = metasoma thumb|The metasoma is clearly visible on this ant: it is the posterior section, including the petiole (insect)|petiole. The metasoma is the posterior part of the body, or tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the mesosoma. In insects, it contains most of the digestive tract, respiratory system, and circulatory system, and the apical segments are typically modified to form genitalia. In a few of the most primitive insects (the Archaeognatha), the metasomal segments bear smal

modified hairs on Apoidea body

ventral portion of a segment of an arthropod thorax or abdomen

mouthpart of an arthropods

A sensillum (plural sensilla) is an arthropod sensory organ protruding from the cuticle of exoskeleton, or sometimes lying within or beneath it. Sensilla appear as small hairs or pegs over an individual's body. Inside each sensillum there are two to four sensory neurons. These neurons, or receptors, gather information about environment the arthropod is in:

mouthpart of insects and crustaceans

one of two pairs of structures on arthropod heads

in arthropods, a pair of mouthparts used either for biting or cutting and holding food

organ for nutrient storage and conversion in arthropods

The mesosoma is the middle part of the body, or tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the metasoma. It bears the legs, and, in the case of winged insects, the wings.

thumb|Four trichobothria on the second leg of the spider Paratropis tuxtlensis Trichobothria (singular trichobothrium) are elongate setae ("hairs") present in arachnids, various orders of insects, and myriapods that function in the detection of airborne vibrations and currents, and electrical charge. In 1883, Friedrich Dahl observed that they were deflected by the sound waves from a violin and labelled them 'hearing hairs'.

major structure of the invertebrate central nervous system

the head section of an arthropod

outermost tissues of arthropods

thumb|One of two gonopods of the greenhouse millipede (Oxidus gracilis). Scale bar: 0.2 mm or approximately 1/127 in Gonopods are specialized appendages of various arthropods used in reproduction or egg-laying. In males, they facilitate the transfer of sperm from male to female during mating, and thus are a type of intromittent organ. In crustaceans and millipedes, gonopods are modified walking or swimming legs. Gonopods may be highly decorated with elaborate structures which may play roles in sperm competition, and can be used to differentiate and identify closely related species. Gonopods g

pair of structures in the brain of arthropods and some annelids

The tentorium (plural tentoria) is a term used to refer to the framework of internal supports within an arthropod head. The tentorium is formed by ingrowths of the exoskeleton, called apodemes, which fuse in various ways to provide rigid support for the muscles of the head.

thumb|right|The head of a mantis showing the black pseudopupil in its compound eyes thumb|right|The eye of a mantis shrimp has three regions, each with its own pseudopupil.

stretch receptor organs